VM doesn't see DHCP server...

[Sheppy]

Hi,
I've tried to find answers on this and while there's quite a lot of stuff about, nothing works or makes sense for my setup.
Server 2016 Hyper-V Datacentre with with 2x/3x nic's, one for OS and the others or VM network access. At some point, I suspect after an update, VM's (servers and workstations) stopped seeing our DHCP servers (Server 2016). They always used to see out DHCP servers, nothing has changed, our network setup is really simple, no VLANS etc.
But VM's will now not connect to our network unless I assign a static IP, they just don't see either of our 2x DHCP servers, it's like they're being blocked. I've tried disabling AV and local firewalls, different virtual switches going to different physical switches, different host servers etc. If I plug anything physical into our network then they see our DHCP servers immediately, and VM's used to with our Hyper-V hosts, but at some point over the last six to twelve months or so (I think) something changed and I can't figure out what. Any help or advice would be gratefully received.
FYI, we have a small number of Windows 10 VM's that were build a while ago and they all still have their DHCP addresses, and continue to renew their leases. It just seems to be new VM's that are affected.
Thanks,
John

 

[DavidWJohnston]

It sounds like perhaps your DHCP scope has exhausted all available IPs? So any new device that doesn't already have a lease cannot acquire one.

Check the DHCP logs on your server(s) and if you see nothing, try a packet trace to see if the broadcast is being received at the DHCP server.

 

[Sheppy]

It sounds like perhaps your DHCP scope has exhausted all available IPs? So any new device that doesn't already have a lease cannot acquire one.

Check the DHCP logs on your server(s) and if you see nothing, try a packet trace to see if the broadcast is being received at the DHCP server.

Hi. Sorry for not replying sooner. You were in fact right. Our DHCP server wasn't working correctly and while it was showing availability, it wasn't issuing any. I had wrongly assumed it was a problem with our hyper-v servers as the various physical test machines we used all worked, but it transpired that if they had been previously connected then they would get an address. All a bit weird. But easily solved. Thank you.